(none)

John,
This can sometimes happen if the temperature of the run is too cool -
the CsCl precipitates. Are you regulating the temperature at something
around 23*C? Also, if you have any evaporation (tubes not completely
sealed?), the CsCl can come out of solution. I've seen both of these
problems occur.
Bob Gross
Dartmouth - Molecular Genetics Center, Biological Sciences
bob.gross at dartmouth.edu